Support GFM admonitions

[henryiii]

Context

See executablebooks/MyST-Parser#845. Basically this:

> [!NOTE]
> This is a note

Looks like this on GitHub:

Note

This is a note

It was suggested in that issue that the implementation should start here.

Proposal

This is a feature of GFM, so it should be supported.

Tasks and updates

No response

[KyleKing]

Hi @henryiii, you can format Github Admonitions today with mdformat-gfm-alerts (https://github.com/KyleKing/mdformat-gfm-alerts?tab=readme-ov-file#mdformat-gfm-alerts)!

Let me know if you run into any issues

[henryiii]

This is only for formatting? Is there also a way to use it in myst/markdown-it-py/jupyter-book?

[KyleKing]

If you install the package in the environment, the Renderer should be auto-discovered. There is just one issue with removing the outer block quote that I'll solve eventually and I'm open to PRs: https://github.com/KyleKing/mdformat-gfm-alerts?tab=readme-ov-file#html-rendering